Sorbic acid is a material of known commercial uses which is available through a process based on the reaction of ketene with crotonaldehyde. The process is effective but its economics depend upon the cost and availability of reactant materials and is also encumbered with formation of undesirable tars. Various dehydrogenation processes are known for dehydrogenating alkanes to alkenes and alkenes to alkadienes as well as some oxidative dehydrogenation processes disclosed as dehydrogenating saturated acid esters to alkenoic acid esters, see U.S. Pat. No. 3,652,654. Various dehydrogenation catalysts are also known.